Help with old, rusted cast iron toilet flange

I've been living in my house about 5 years. Finally decided to replace an old toilet in our bathroom.

When I pulled up the old toilet, I was facing a very corroded old cast iron toilet flange and there was no evidence of ANY wax ring having ever been used...

The pipe itself seems to be good, its just the ring part of the flange that is hosed. I purchased a new PVC flange made to be installed into cast iron pipe, but (after lots of research) the method of removing the old iron flange doesn't seem to apply - I don't see any traces of lead, oakham etc, and inside the pipe I don't see any seems or ridges to indicate it's a flange installation - it all seems to be the same piece of pipe.

If it's any help, the house was build in 1950 and I suppose the flange is original to the house.

I purchased a ring replacement (see pic) and tried installing that - the concrete was weak around it so have re-concreted around the ring and am waiting for that to set before trying the ring. My only concern is the ring will sit on top of the pipe end and may be a little too high.

I'm looking for your help on how to proceed... Go with the ring, try breaking/grinding the pipe to be flush with floor and using PVC, etc....

In the pic below, you will see what remains of the original flange is still very sturdy - the rest was corroded and came off when attempting to pry up what I thought would be a cast iron flange with lead solder/oakham install.

Also, its a 2nd floor bathroom with the pipe in a "concrete box" - access to the underside is pretty much a no-go without destroying my kitchen!

After a lot of grinding and performing a lot of clean up using a heavy duty metal brush, to my surprise I did actually find lead, and was able to remove the old flange - it wasn't a "one-piece" after all.

I guess the point is that regardless of how much it doesn't look like a seperate flange, keep digging and cleaning up. It probably is deep-deep down under all that rust, muck and old wax!!

New ring fits and works like a charm now, just need to wait for the concrete to dry...